Add type definition and writeErrorToResponse

README.md

@@ -46,6 +46,29 @@ app.use(errorHandler({
 app.listen(3000);
 ```
 
+The module also exports `writeErrorToResponse`, a non-middleware flavor of the
+error handler:
+
+```js
+const http = require('http');
+const writeErrorToResponse = require('strong-error-handler')
+  .writeErrorToResponse;
+const errHandlingOptions = {debug: process.env.NODE_ENV === 'development'}
+
+http
+  .createServer((req, res) => {
+    if (errShouldBeThrown) {
+      writeErrorToResponse(
+        new Error('something went wrong'),
+        req,
+        res,
+        errHandlingOptions,
+      );
+    }
+  })
+  .listen(3000);
+```
+
 In LoopBack applications, add the following entry to `server/middleware.json`:
 
 ```json

index.d.ts

@@ -0,0 +1,64 @@
+// Copyright IBM Corp. 2018. All Rights Reserved.
+// Node module: strong-error-handler
+// This file is licensed under the MIT License.
+// License text available at https://opensource.org/licenses/MIT
+
+// Type definitions for strong-error-handler 3.x
+// Project: https://github.com/strongloop/strong-error-handler
+// Definitions by: Kyusung Shim <https://github.com/shimks>
+// TypeScript Version: 3.0
+
+import * as Express from 'express';
+
+export = errorHandlerFactory;
+
+/**
+ * Creates a middleware function for error-handling
+ * @param options Options for error handler settings
+ */
+declare function errorHandlerFactory(
+  options?: errorHandlerFactory.ErrorHandlerOptions
+): errorHandlerFactory.StrongErrorHandler;
+
+declare namespace errorHandlerFactory {
+  /**
+   * Writes thrown error to response
+   * @param err Error to handle
+   * @param req Incoming request
+   * @param res Response
+   * @param options Options for error handler settings
+   */
+  function writeErrorToResponse(
+    err: Error,
+    req: Express.Request,
+    res: Express.Response,
+    options?: ErrorWriterOptions
+  ): void;
+
+  /**
+   * Error-handling middleware function. Includes server-side logging
+   */
+  type StrongErrorHandler = (
+    err: Error,
+    req: Express.Request,
+    res: Express.Response,
+    next: (err?: any) => void
+  ) => void;
+
+  /**
+   * Options for writing errors to the response
+   */
+  interface ErrorWriterOptions {
+    debug?: boolean;
+    safeFields?: string[];
+    defaultType?: string;
+    negotiateContentType?: boolean;
+  }
+
+  /**
+   * Options for error-handling
+   */
+  interface ErrorHandlerOptions extends ErrorWriterOptions {
+    log?: boolean;
+  }
+}

lib/handler.js

@@ -23,7 +23,7 @@ function noop() {
  * @param {Object} options
  * @returns {Function}
  */
-exports = module.exports = function createStrongErrorHandler(options) {
+function createStrongErrorHandler(options) {
   options = options || {};
 
   debug('Initializing with options %j', options);
@@ -32,31 +32,47 @@ exports = module.exports = function createStrongErrorHandler(options) {
   var logError = options.log !== false ? logToConsole : noop;
 
   return function strongErrorHandler(err, req, res, next) {
-    debug('Handling %s', err.stack || err);
-
     logError(req, err);
-
+    writeErrorToResponse(err, req, res, options);
-    if (res._header) {
-      debug('Response was already sent, closing the underlying connection');
-      return req.socket.destroy();
-    }
-
-    // this will alter the err object, to handle when res.statusCode is an error
-    if (!err.status && !err.statusCode && res.statusCode >= 400)
-      err.statusCode = res.statusCode;
-
-    var data = buildResponseData(err, options);
-    debug('Response status %s data %j', data.statusCode, data);
-
-    res.setHeader('X-Content-Type-Options', 'nosniff');
-    res.statusCode = data.statusCode;
-
-    var sendResponse = negotiateContentProducer(req, warn, options);
-    sendResponse(res, data);
-
-    function warn(msg) {
-      res.header('X-Warning', msg);
-      debug(msg);
-    }
   };
 };
+
+/**
+ * Writes thrown error to response
+ *
+ * @param {Error} err
+ * @param {Express.Request} req
+ * @param {Express.Response} res
+ * @param {Object} options
+ */
+function writeErrorToResponse(err, req, res, options) {
+  debug('Handling %s', err.stack || err);
+
+  options = options || {};
+
+  if (res._header) {
+    debug('Response was already sent, closing the underlying connection');
+    return req.socket.destroy();
+  }
+
+  // this will alter the err object, to handle when res.statusCode is an error
+  if (!err.status && !err.statusCode && res.statusCode >= 400)
+    err.statusCode = res.statusCode;
+
+  var data = buildResponseData(err, options);
+  debug('Response status %s data %j', data.statusCode, data);
+
+  res.setHeader('X-Content-Type-Options', 'nosniff');
+  res.statusCode = data.statusCode;
+
+  var sendResponse = negotiateContentProducer(req, warn, options);
+  sendResponse(res, data);
+
+  function warn(msg) {
+    res.header('X-Warning', msg);
+    debug(msg);
+  }
+};
+
+exports = module.exports = createStrongErrorHandler;
+exports.writeErrorToResponse = writeErrorToResponse;

package.json

@@ -17,6 +17,7 @@
     "posttest": "npm run lint"
   },
   "dependencies": {
+    "@types/express": "^4.16.0",
     "accepts": "^1.3.3",
     "debug": "^3.1.0",
     "ejs": "^2.6.1",

test/handler.test.js

@@ -78,7 +78,8 @@ describe('strong-error-handler', function() {
       request.get('/').expect(
         507,
         {error: {statusCode: 507, message: 'Insufficient Storage'}},
-        done);
+        done
+      );
     });
   });
 
@@ -145,7 +146,8 @@ describe('strong-error-handler', function() {
     it('handles array argument', function(done) {
       givenErrorHandlerForError(
         [new TypeError('ERR1'), new Error('ERR2')],
-        {log: true});
+        {log: true}
+      );
 
       request.get('/api').end(function(err) {
         if (err) return done(err);
@@ -565,8 +567,7 @@ describe('strong-error-handler', function() {
             );
             done();
           });
-      }
+      });
-    );
 
     it('HTML-escapes all 5xx response properties in development mode',
       function(done) {
@@ -582,8 +583,7 @@ describe('strong-error-handler', function() {
             /500(.*?)a test error message<img onerror=alert\(1\) src=a>/,
             done
           );
-      }
+      });
-    );
 
     it('contains subset of properties when status=4xx', function(done) {
       var error = new ErrorWithProps({
@@ -750,8 +750,7 @@ describe('strong-error-handler', function() {
         request.get('/')
           .set('Accept', 'text/html')
           .expect('Content-Type', /^application\/json/, done);
-      }
+      });
-    );
 
     it('chooses resolved type when negotiateContentType=false + not-supported',
       function(done) {
@@ -762,8 +761,7 @@ describe('strong-error-handler', function() {
         request.get('/')
           .set('Accept', 'text/html')
           .expect('Content-Type', /^text\/html/, done);
-      }
+      });
-    );
 
     it('chooses default type when negotiateContentType=false + not-supported ',
       function(done) {
@@ -773,8 +771,7 @@ describe('strong-error-handler', function() {
         });
         request.get('/')
           .expect('Content-Type', /^application\/json/, done);
-      }
+      });
-    );
 
     it('honors order of accepted content-types of text/html', function(done) {
       givenErrorHandlerForError(new Error('Some error'), {